DIY, is smallest problem.
I've made clones, but I need a sample first.
Perhaps it is nothing special, like many other expensive things, All done with good marketing.
Do U have this drawing?
If U think that is illegal, everybody can PM me!

Had a look at your website, I have a very similar ham radio to yours, tube, it looks the same but mine is 200 Watts if I recall correctly, I havent used it for 15 years, a gift from my father. Works very well, and at that time I expanded the frequencies to include cb radio frequencies too. CB radios were good, but in my country of birth it was banned to have more than 12 watts so this was the solution.